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Apoptotic membrane blebbing is regulated by myosin light chain phosphorylation
J C Mills1, N L Stone, J Erhardt
1Department of Pharmacology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
The Journal of Cell Biology
|March 14, 1998
Summary
Apoptosis involves cell shrinkage and membrane blebbing. This study reveals myosin light chain kinase (MLCK) and Rho signaling pathways are critical for these morphological changes during programmed cell death.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Apoptosis execution involves cell shrinkage, chromatin condensation, and DNA fragmentation.
- Mechanisms driving these final stages of cell death, particularly membrane blebbing, are poorly understood due to rapid, asynchronous cellular events.
Purpose of the Study:
- To elucidate the signaling mechanisms responsible for membrane blebbing during apoptosis.
- To establish a model system for studying the synchronous execution phase of apoptosis.
Main Methods:
- Utilized a caspase inhibitor (z-VAD-FMK) to synchronize apoptotic cells and induce membrane blebbing.
- Screened kinase inhibitors, performed immunoprecipitation of myosin II, and used C3 transferase to investigate signaling pathways.
- Disrupted the actin cytoskeleton to assess its role in blebbing.
Main Results:
- Myosin light chain kinase (MLCK) inhibitors significantly reduced membrane blebbing.
- Myosin regulatory light chain (MLC) phosphorylation increased in blebbing cells and was inhibited by MLCK inhibitors.
- Rho signaling and actin cytoskeleton integrity were found to be essential for apoptotic membrane blebbing.
Conclusions:
- MLC phosphorylation, mediated by MLCK and Rho signaling, is critical for apoptotic membrane blebbing.
- Actin/myosin II interactions drive cell contraction and membrane blebbing during apoptosis.
- The developed model system facilitates further research into signaling pathways during apoptosis execution.